RockRockss

A rock is a hard material made of one or more minerals

Or anything that when you pick it up and throw it at someone it produces the reaction: "Owww! Why did you hit me in the head with a rock?"

The dictionary is no use here: Rock n: a large mass of stone; a concreted mass of

stony material; consolidated mineral matter I love this one: something like a rock in firmness

By the way, a stone is " a piece of rock"! A rock can be made of only one mineral entirely (monomineralic) or a mixture of many minerals (polymineralic)

3 groups of rocks3 groups of rocks

• A rock is a group of minerals joined together in some way– IgneousIgneous – formed by the cooling &

solidification of molten rock (magma)– SedimentarySedimentary – formed by the compaction

& cementation of layers of sediment (rock fragments, organic remains, chemical deposits)

– MetamorphicMetamorphic – formed when existing rocks are CHANGED by intense heat & pressure

Igneous Igneous Rocks Rocks

ESRT ESRT page 6page 6

Igneous rocks form from Igneous rocks form from the cooling or the cooling or SOLIDIFICATIONSOLIDIFICATION of magma (melted rock) of magma (melted rock)

The The RECRYSTALLIZATIONRECRYSTALLIZATION of minerals is of minerals is evident in Igneous Rocksevident in Igneous Rocks

• Magma is a mixture of liquid rock, crystals, and gas

• It is characterized by a wide range of chemical compositions, with high temperature, and  properties of a liquid

• Magmas are less dense than surrounding rocks, and will therefore move upward

LIQUID HOT MAGMALIQUID HOT MAGMA

• If magma makes it to the surface it will erupt and later crystallize to form an extrusive or volcanic rock

• If it crystallizes before it reaches the surface it will form an igneous rock at depth called a plutonic or intrusive igneous rock

• Because cooling of the magma takes place at a different rate, the crystals that form and their texture exhibit different properties

intrusive igneous rocksintrusive igneous rocks• Form by the

cooling of magma UNDERGROUNDUNDERGROUND– “IN” –trusive

Also known as PLUTONIC

• Underground cooling is SLOWERSLOWER– Rock crystals are crystals are

LARGELARGE & have a coarse texture

gabbrogabbro

granitegranite

pegmatitepegmatite

Granite Mineral CompositionGranite Mineral Composition

extrusive igneous extrusive igneous rocksrocks

• Forms from the cooling of LAVALAVA (magma that has reached earth’s surface)

Lava flows forming Lava flows forming extrusive igneous rocks extrusive igneous rocks

(obsidian)(obsidian)

• Cools QUICKLYQUICKLY (exposed to colder air)– Rock crystals are

SMALLSMALL and rocks have a fine/glassy texture

Shiprock, NMShiprock, NM

An intrusive igneous rock formation called a An intrusive igneous rock formation called a “volcanic neck”“volcanic neck”

Pumice is an Extrusive Igneous Rock that is Pumice is an Extrusive Igneous Rock that is VESICULAR (has gas pockets).VESICULAR (has gas pockets). Because Because

pumice formed so quickly, the rock formed pumice formed so quickly, the rock formed around the pockets of gas, creating “holes” in around the pockets of gas, creating “holes” in the rock. This allows the rock to float in water the rock. This allows the rock to float in water

because of its lower density!because of its lower density!

Key idea:Key idea:

The The texturetexture of the of the igneous rock is igneous rock is

determined by the size, determined by the size, shape, and shape, and

arrangement of the arrangement of the mineral crystalsmineral crystals!!

types of magmatypes of magma• FELSIC MAGMAFELSIC MAGMA

– Light colored– Thick (high

viscosity)– Contains high

amounts of silica•Granite

• MAFIC MAGMAMAFIC MAGMA– Dark colored– Thin (low

viscosity)– Contains high

amount of magnesium & iron•Basalt

the “bells & whistles” for the “bells & whistles” for identifying an IGNEOUS identifying an IGNEOUS

rockrockIgneous rocks have obvious CRYSTALSRYSTALS!!!

So if you see minerals, it’s probably igneous!

sedimentarsedimentary rocksy rocks

Formation:Formation:

• Sedimentary rocks form from the COMPACTION & CEMENTATIONCOMPACTION & CEMENTATION of rock fragments

• Rock fragments are “glued” together by a matrix of calcite, silica, or iron oxide

3 types of sedimentary 3 types of sedimentary rocksrocks

• CLASTICCLASTIC – formed from fragments of other rocks– Sandstone, Conglomerate

• CHEMICALCHEMICAL – formed from the mineral precipitates of evaporated seawater– Rock Salt

• ORGANICORGANIC – formed from the remains of plants & animals with rock fragments– Coal, Fossil Limestone

CLASTICCLASTIC

• Formed when rock fragments & sediment are carried & deposited by WIND, GLACIERS, & RUNNING WATERRUNNING WATER

• Sediments are DEPOSITEDDEPOSITED, then COMPACTEDCOMPACTED & finally CEMENTEDCEMENTED together

• Fragments that make up these rocks come in many shapes & sizes

• They are formed from PRE-EXISTING rock that has been eroded!!!

• Can be igneous, sedimentary, or metamorphic fragments

Most sediment is carried byMost sediment is carried byRunning Water!Running Water!

• The further water carries the sediment, the more ROUND & ROUND & SMOOTHSMOOTH the particle becomes

• When a stream slows down, it drops the LARGESTLARGEST particles first, & the SMALLESTSMALLEST last (HORIZONTAL SORTING)(HORIZONTAL SORTING)

BrecciaBreccia – very large sediments that are angular

(note hammer for size reference)

ConglomerateConglomerate – large

sediments that are rounded (have been

transported by a stream!)

STRATIFICATIONSTRATIFICATION

• Sandstones & Siltstones form from smaller sediments that tend to create “layers” of sediments in rocks

• This is known as STRATIFICATIONSTRATIFICATION (layering)

• There will be layers of SIMILARSIMILAR colored minerals

Angel’s Landing, Zion Angel’s Landing, Zion Nat’l Park, UtahNat’l Park, Utah – note

rock layers (extra note – this is where my husband proposed to me – at the

very top!)

Mrs. Blanarovich

getting proposed

to!

Red Sandstone, UtahRed Sandstone, Utah – note distinct LAYERING of sediments (sand)

Horseshoe Bend, Utah

Grand Canyon Nat’l Park, ArizonaGrand Canyon Nat’l Park, Arizona – sedimentary rock formation at its best! The canyons were formed by the Colorado River

cutting into the rock layers over time!

CHEMICALCHEMICAL

• Formed when dissolved minerals in seawater are deposited (seawater seawater evaporates,evaporates, leaving the minerals behind)

• Usually old swamps, seas, or lakes evaporate

• Also known as CRYSTALLINECRYSTALLINE because of the fine crystals – Limestone, Rock Salt, Rock Gypsum (sheetrock)

Salt “Mines”Salt “Mines” - Rock Salt is being formed as the salt water evaporates

from the sea.

““Devil’s Golf Devil’s Golf Course”Course” – millions of years ago this was a sea of salt water. It has been

evaporating over time…

…and has formed

“pockets” of chemical

limestone, rock salt, and rock gypsum!

ORGANICORGANIC

• Formed from the remains of plants & animals that are compacted– Fossil LimestoneFossil Limestone – formed when

shell remains of marine organisms are cemented in fragments•Shells are made of CALCITE which reacts

with acid and is a natural “cement”

Brachiopod fossils in limestone Imprint

of a leaf

Trilobite fossils – over 250 MILLION years old!!!

If peat at the bottom of a If peat at the bottom of a swamp is buried & swamp is buried &

compressed, coal may compressed, coal may formform Coal – Coal –

note note distinct distinct layering layering of peatof peat

bells & whistles for bells & whistles for sedimentary rock sedimentary rock

identification!identification!• StratificationStratification –

“layering” of sediments

• FossilsFossils – actual remains or imprints

• Ripple marks, mud cracks, etc…

Ripple Marks in the Shale from

running water as the

rock was forming!

ESRT page 7ESRT page 7

metamorphic metamorphic rocksrocks

ESRT page 7ESRT page 7

Key Key ideasideas

• Formed when existing rocks are changed by HEAT & PRESSUREHEAT & PRESSURE

• The new rocks resemble the “parent” rock

• IMPORTANT- THE ORIGINAL ROCK CANNOT MELTCANNOT MELT WHEN IT BECOMES METAMORPHIC! (If it melts, it’s igneous!)

Types of Types of metamorphismmetamorphism

• REGIONALREGIONAL• Large areas of

rock are changed by HEAT & PRESSURE

• CONTACTCONTACT• Magma touches

layers of rock and the HEAT causes the rock layers to change

Identifying Identifying characteristicscharacteristics

• FOLIATIONFOLIATION – mineral alignmentmineral alignment – the minerals in the rock are layered, which facilitates breakage along flat planes

• BANDINGBANDING – alternating layers of different colored mineralsdifferent colored minerals– These bands are usually distorted from

the heat & pressure

Foliation – note the Foliation – note the “scratches” in the “scratches” in the

rock – this is mineral rock – this is mineral alignment!alignment!

More More foliatiofoliatio

n – n – slate & slate & phyllitephyllite

Banding – mica Banding – mica schistschist

ExcellenExcellent t

example example of of

banding banding & &

distortiodistortion – this n – this

is is GNEISS GNEISS

Metamorphic mountains Metamorphic mountains formed from regional formed from regional

metamorphismmetamorphism

Alaska’s Copper Mountain – contact Alaska’s Copper Mountain – contact metamorphismmetamorphism

the bells & whistles for the bells & whistles for metamorphic rock metamorphic rock

identificationidentification• FOLIATIONFOLIATION – mineral alignment –

look for “scratches” in the rocks

• BANDINGBANDING – layers of DIFFERENT DIFFERENT COLORSCOLORS – not to be confused with sedimentary layers!!!!!! (these will be obviously different parent rock layers)

When I was young, liquid granite I was diagnosed schizophrenic Neither feldspar, nor mica, nor quartz But the sum of the three Bonded igneously That means melted together for life

Well, I was hot and dejected Oh, I was injected Under layers and layers of dirt But, it was there that I changed All my crystals rearranged Into G-N-E-I-S-S, gneiss

So, take a look, and you'll see That I'm not what I used to be I've been touched metamorphically All the heat and the pressure Have changed me forever So don't take me for granite, I'm gneiss

Well, I wasn't to been seen Until time changed the scene Exposing my face to the sun But, now its here that I sit Being worn down bit by bit Oh, erosion is wearing me down

Refrain

So, be aware, have a look Underground or underfoot For that beautiful pinky-gray face The Canadian shield Holds a magnamous yield Of the rock that was changed into gneiss

Refrain

The GNEISS The GNEISS SONGSONG

OkayOkay……

Let’s sum Let’s sum up!up!

There are 3 classifications of There are 3 classifications of ROCKSROCKS

• IgneousIgneous – formed by the cooling of magma (melted rock)

• SedimentarySedimentary – formed by compaction & cementation of rock fragments

• MetamorphicMetamorphic – formed by heat & pressure changing existing rocks

• The ROCK CYCLE shows how each The ROCK CYCLE shows how each type of rock forms & how each rock type of rock forms & how each rock can change into a different type of can change into a different type of

rock!rock!

The ROCK CYCLE is also The ROCK CYCLE is also found in your ESRT found in your ESRT

page 6!page 6!

Remember the “bells & Remember the “bells & whistles” when identifying whistles” when identifying

rocks!rocks!

• IgneousIgneous – obvious crystals of – obvious crystals of different mineralsdifferent minerals

• SedimentarySedimentary – stratification, – stratification, fragments, fossilsfragments, fossils

• MetamorphicMetamorphic – foliation, – foliation, bandingbanding